Swimming pool monitor



3% 3, 19% E. A. KOLM SWIMMING POOL MONITOR Filed April 28, 1964 ERIC A. KOLM United States Patent 3,273,138 SWllMMING PQOL MONITOR Eric A. Kolm, Brookline, Mass, assignor to Sonus Corporation, Cambridge, Mass. Filed Apr. 28, 1964, Ser. No. 363,206 7 Claims. (Cl. 340-261) This invention relates to a swimming pool monitor. It relates more particularly to a swimming pool monitor capable of detecting sounds and turbulence caused by children or animals jumping or falling into an unattended swimming pool and giving a warning signal in response thereto. In addition, the monitor permits someone at a remote location to actually listen to the goings on at the pool and thereby determine the nature of the disturbance and extent of the emergency.

One difiiculty with conventional swimming pool monitor or alarm systems is that while many of them are able :to sound an alarm when someone or something jumps or falls into the pool, they do not discriminate between an actual emergency and other disturbances. That is, when they sound an alarm, there is no way for one to determine, without going to the pool, what the object that entered the pool was, or whether there is indeed an emergency situation requiring immediate action.

Also, prior systems are often unable to discriminate between turbulence in the pool caused by wind, rain, falling twigs, etc., and turbulence produced by struggling children and animals. As a result the pool owner may be subjected to a considerable number of false alarms. If the sensitivity of the alarm is reduced, it may fail to register a true emergency.

Accordingly, the main object of this invention is to provide a swimming pool monitor capable of giving an immediate warning signal whenever an object enters intentionally or inadvertently an unattended swimming 001. p A further object of this invention is to provide a swimming pool monitor which, after sounding an alarm can be used to listen to the disturbance so that the pool owner can ascertain exactly what is happening by the sounds emanating from, in and around the swimming pool. Moreover, with this feature of the invention, accidents can actually be prevented. For example, by operating the monitor in the listening mode, a mother can detect potential danger resulting from rough play in or near the pool without ever having to be physically present.

A still further object of this invention is to provide a swimming pool monitor which substantially eliminates false alarms because it is nonresponsive to most spurious sounds and vibrations in and around the pool.

It is another more specific object of the invention to provide a swimming pool monitor which is relatively easy to manufacture, using inexpensive yet reliable components; which is easily installed being powered by the usual house supply; and which requires substantially no maintenance or upkeep.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, the combination of elements, and arrangement of parts, which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in accordance with the accompanying drawing, which is a schematic diagram of a swimming pool monitor embodying the principles of the invention.

In general, my swimming pool monitor employs an underwater microphone or hydrophone 10 capable of 3,273,138 Patented Sept. 13, 1966 being submerged in the swimming pool and picking up underwater vibrations. These vibrations may be caused by children or animals thrashing in the water or even by voices or other noises in and around the pool. The output of the hydrophone is coupled through a filter-preamplifier 12 and fed to a detector circuit 14 which senses the amplified signals. The detector circuit 14 actuates a switch energizing an oscillator-amplifier 18 circuit and the latter produces an audible alarm via an associated speaker 20. The alarm will continue until the detector circuit is manually reset by the pool owner, even though the initiating vibrations in the pool cease.

The swimming pool monitor also has provision for switching from the aforesaid alarm or warning mode to a listening mode whereby the amplified signals from the hydrophone 10 are caused to bypass the detector circuit 14 and are connected directly to the oscillator-amplifier circuit 18. In this listening mode the circuit 18 amplifies the input signal and feeds it directly to loud speaker 20. Thus, someone listening to the monitor at a location remote from the pool can actually hear voices and other sounds emanating from around the pool and determine what is happening.

Filter circuits are provided in the preamplifier stage 12 of the monitor to shape the frequency response thereof depending on whether the monitor is in the alarm or listening mode. When the monitor is in the listening mode, the preamplifier 12 passes the full voice range of frequencies. On the other hand, when it is in the warning or alarm mode, high frequencies caused by sirens, whistles, etc. and low frequencies caused by thunder, traffic, etc. are filtered out so that the monitor is made less susceptible to false alarms. A sensitivity control compensates for the ambient background noise level that may be present around a given pool installation.

The invention is embodied in a simple unit which may be installed with a minimum of effort and powered by a conventional power supply indicated at 21 connected to the standard volt A.C. house supply or, alternatively by batteries.

More specifically, hydrophone 10 is preferably one of the piezoelectric variety capable of producing electrical signals in response to sound vibrations impinging the transducer. The hydrophone 10 is adapted to be submerged in the swimming pool and supported below the water and away from the side of the pool by a bracket (not shown) attached to the side of the pool. A shielded coaxial cable 22 connects the transducer 10 with the filterpreamplifier 12 which is mounted along with the other elements of the monitor within a single cabinet conveniently located in the home of the pool owner.

The filter-preamplifier 12 has three transistor stages comprising three similar n-p-n transistors 24, 26 and 28. These transistors are connected in the common-emitter configuration and have bypassed emitter resistors. The collectors 30, 32 and 34 of the transistors are connected through resistors 36, 38 and 430, respectively, to power supply 21.

Resistor 38 is preferably a potentiometer having an adjustable center tap 42 whose adjustment controls the gain of the preamplifier 12. Specifically, the potentiometer 38 provides a means for controlling the sensitivity of filter preamplifier 12 so that the system responds only to those signals produced by sounds above the ambient or "background noise level in the vicinity of the pool.

A coupling capacitor 44 and series resistance 46 are connected between the inner conductor of coaxial cable 22 and the base 48 of transistor 24. The outer conductor or sheath of cable 22 is grounded. A relatively small coupling capacitor 50 is connected between collector 30 of transistor 24 and the base input 52 of transistor 26. A single pole switch 54a and a relatively large capacitor 56 in series therewith are connected in parallel with capacitor 50. Switch 54:: is movable between two positions, A and 'L. When switch 54a is in the A position, the relatively large capacitor 56 is connected in parallel with the small capacitor 50. In the L position the branch containing the large capacitor 56 is open-circuited and the coupling between transistors 24 and 26 is entirely through the small capacitor 50.

There is a similar coupling arrangement between transistors 26 and 28. More particularly, a two-position switch 54b has its common terminal connected to the center tap 42 of potentiometer 38. Switch 54b operates between two positions or terminals, A and L. A relatively large capacitor 58 is connected between the L terminal of switch 541) and the base 60 of transistor 28. A smaller capacitor 62 is connected between the A terminal and the base 60. In addition, a capacitor 64 is connected between the A terminal of switch 54b and ground. In practice, the switches 54a and 54b are ganged together and thus operate in unison.

When the switches 54a and 5412 are in the A position, electrical signals produced by the transducer in response to sound vibrations in the water are amplified by transistor 24 and coupled through the small capacitor 50 to transistor 26. The capacitance of the capacitor 50 is so related to the resistances associated therewith, that they combine as a high-pass R.C. filter which filters out electrical signals falling below a predetermined frequency. The signals passed by capacitor 50 are further amplified by transistor 26 and are coupled through the other small capacitor 62 to the transistor 28. Capacitor 62 and associated resistances also act to filter out low frequency signals. The two high-pass filters combine to filter out signals produced by such sounds as thunder, trafiic, airplanes, etc. having nothing to do with activities at the swimming pool.

In addition, with the switch 54b in the A position, the capacitor 64 and the series resistances associated therewith operate as a low-pass filter reducing electrical signals caused by high frequency background sounds such as whistles, high-pitched squeals, etc. picked up by transducer 10.

In actual practice, the circuit parameters of filter preamplifier 12 are selected so that the amplifier passes signals in a band of about 500-900 cycles extending upwardly from approximately 2500 cps. The filter preamplifier 12 has a bandwidth of approximately 500-900 cycles. This particular frequency range has been found to include most of the sounds produced by a person or animal thrashing or struggling in water as well as those sounds caused by a person choking or gasping underwater, but to exclude most of the usual background sounds and noises which have nothing to do with the pool and which tend only to cause false alarms.

When the switches 54a and 54b are in the L position, on the other hand, the electric signals from collector are coupled through a relatively large capacitance, consisting primarily of capacitor 56, to the base 52 of transistor 26. Also, the output of transistor 26 taken from collector 32 is caused to bypass capacitors 62 and 64 and is coupled through the large capacitor 58 directly to the base 60 of transistor 28. As a result, the pass band of the filter amplifier 12 is increased considerably. The frequencies comprising substantially the entire voice range are then amplified by filter-preamplifier 12.

The output of preamplifier 12, taken from the collector 34 of transistor 28, is fed to switch 54c. This switch also has two terminals or positions A and L. The A terminal is connected to the detector circuit 14, while the L terminal is connected to the oscillator-amplifier circuit 18 that will be described more particularly later.

The detector circuit 14 comprises a diode 66 coupled to the collector 34 by a DC. blocking capacitor 68. The anode 72 of diode 66 is connected through a DC. blocking capacitor 74 to the base 76 of an n-p-n transistor 78 having a grounded emitter. Resistors 80 and 82 are connected between ground and the cathode 70 and anode 72 respectively, of diode 66 to prevent blocking of the diode by signals rectified thereby.

The collector 84 of transistor 78 is connected through a resistor 86 to a positive terminal of power supply 21. A resistor 83 connected between base 76 and ground, forms a voltage divider with a resistor 96 and the resistance of a relay coil 100 to bias the base-emitter junction of the transistor 78 for normal conduction. The collector 84' is connected also through a resistor 88 to the base 90 of a normally cut off, grounded emitter, n-p-n transistor 92. A normally closed switch 94 connects the collector 98 of transistor 92 to the junction of the resistor 96 and the relay coil 100. Constant voltage is assured the detector circuit 14 by a Zencr diode 102 in supply 21.

The two transistors 78 and 92 form a flip-flop. In the absence of signals from filter-preamplifier 12, the flip-flop is in the one of its stable states in which the transistor 78 is conducting and transistor 92 is cut off by the essentially zero potential of the base 90 resulting from the low collector-emitter resistance in the transistor 78. Thus, substantially no current flows through relay coil 1%.

When switch 540 is in the A position and signals arrive from filter-preamplifier 12, the diode 66 passes only the negative-going portions of the signals to the base input 76 of transistor 78. These portions cut off transistor 78, thereby raising the potential at its collector 84. This increased potential is coupled to the base 90 of transistor 92 causing transistor 92 to conduct. As transistor 92 conducts, the potential at its collector 98 reduces substantially to zero. This reduced potential is coupled back to the base input 76 of transistor '79. The flip-flop is now in its other stable state. The diode 66 prevents positive going portions of signals from reaching the base 76 and thereby returning the flip-flop to its initial state. Consequently the flip-flop remains in its new state, even after the input signals from filter-preamplifier 12 cease.

So long as transistor 92 conducts, sutficient current flows through coil 100 to actuate an associated relay switch 100a located in oscillator-amplifier circuit 18 and controlling the alarm portion of the monitor. Coil 100 will remain energized until the operator momentarily opens the switch 94. This switch can be mounted at any convenient location in the home. This open-circuits the collector 98 of transistor 92 and causes the flip-flop to switch to its initial state wherein transistor 92 is cut off and transistor 78 conducts. Current then ceases to flow in coil 100 and the associated relay switch 100a opens to shut off the alarm. This normal alarm-oft condition will, of course, persist until the arrival of additional signals from filter-preamplifier circuit 12.

The relay switch 100a is a normally open, single pole switch. It is connected between the A and L terminals of a two-position switch 54d whose common terminal is connected to the power supply 21.

The L terminal of switch 54d is connected also through a resistor 108 to the collector 110 of an n-p-n transistor 112. Transistor 112 is connected in the common emitter configuration and has a conventional bypassed emitter resistor and stabilizing and biasing resistors of a conventional amplification stage much like those in filter-preamplifier 12.

A coupling capacitor 114 is connected between the L terminal of switch 54c and base 116 of transistor 112. When switch 540 is in the L position, the signals from filter-preamplifier 12 bypass the detector circuit 14 and are coupled directly to the base input 116 of transistor 112. However, when switch 540 is in the A position, no signals are fed to the base of transistor 112.

It will be apparent that the switch 54d and relay switch 100a control the power applied to transistor 112. When switch 54d is in the A position, power is applied to transistor 1112 only when relay switch 100a is closed by the energizing of coil 100 in the detector circuit 14. But when switch 54d is in the L position, the relay switch 10001 is bypassed and the voltage from power supply 21 is applied directly to transistor 112 independently of the state of the detector circuit 14.

The output from the collector 110 of transistor 112 is coupled through a capacitor 118 to the base 120 of a p-n-p transistor 122. Transistor 122 has its emitter 124 connected through a resistor 126 to the power supply 21. An A.C. path to ground is provided the emitter 124 through a capacitor 127. Resistors 128 and 130, in series between the power supply 21 and ground, form a voltage divider biasing the emitter 124 positive with respect to the base 120.

The primary winding of an output transformer 132 is connected between ground and the collector 134 of transistor 122. The transformer secondary is connected to speaker 20. A capacitor 136 is connected between collector 134 and the emitter 138 of transistor 112 to provide negative feedback.

An R.C. coupling network indicated generally at 140 provides regenerative feedback between the collector 134 of transistor 122 and the base 116 of transistor 112. The feedback network 140 includes a capacitor 142 and a resistor 144 in series therewith, both of which are connected in parallel with a capacitor 146 between collector 134 and the common terminal of a single throw switch 54c. The switch 542 is movable between two terminals A and L, the former of which is connected to the base 116 of transistor 112.

In practice, all of the switches 54a-e are operated in unison between their A positions and their L positions. When switches 54 are in their A positions, the oscillator-amplifier circuit 18 functions as a conventional oscillator by virtue of the network :140. In this mode it can produce an audible whistle or squeal over speaker 20. It cannot oscillate, however, until the relay switch 100a closes to supply power to the first stage transistor 112. This occurs only when current flows in the relay coil 100 in detector circuit 14 pursuant to a change in state of the detector flip-flop circuit as described previously. Once the relay switch 100 closes as aforesaid, the circuit 18 will continue to produce a lound signal over speaker 20 thereby warning the pool owner that someone or something has fallen into or is struggling in the pool. The signal will continue until the relay switch 100a is opened, thereby disabling transistor 112. As mentioned previously, this is brought about by the pool owner or operator momentarily opening the switch 94 in the detector circuit 14.

When the switches 54 are in their L positions, on the other hand, power is supplied to transistor 112 regardless of the condition of detector circuit 14. The feedback loop 140 is open-circuited so that the circuit 18 functions as a conventional two-stage amplifier. The output signals from filter preamplifier 12 are coupled directly to the base 116 of transistor 112. They are amplified by circuit 18 and converted by the speaker 20 into audible sounds which reflect what is going on at the pool. It is a feature of this invention that when the monitor alarm sounds, the pool owner can turn the ganged switches 54 to their L positions and thereby determine the nature of the disturbance at the pool. This feature is particularly useful when the home owner is unable for one reason or another to rush immediately to the pool when the alarm sounds.

The monitor can also be operated for long periods of time in the listening mode with the switches '54 in the L position. Thus a housewife may listen to children playing in and around the swinmming pool. If the play Of course, the monitor can be used also as a simple means of communicating between the area of the pool and the interior of the home.

It will be seen from the foregoing, then, that my swimming pool monitor not only gives a warning alarm when persons approach or enter the swimming pool without authorization, but also enables the homeowner to listen to what is happening at the pool without being physically present there. When the alarm sounds, the homeowner can switch to the listening mode of operation and thereby quickly determine the nature and seriousness of the difiiculty, and be in a much better posit-ion to pro-vide or summon the required assistance.

When the monitor is operating in the alarm mode, its response to sounds in the vicinity of the pool is limited to a relatively narrow band of frequencies which have been found to be particularly indicative of people or animals falling into or struggling in the water. However, when the monitor is operating in its listening mode, its response is altered to permit both high and low frequency sounds to be amplified and reproduced by the speaker 20. Accordingly, the monitor has excellent voice reproduction qualities in its listening mode.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above article without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all the statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention what I claim is new and secured by letters 'Patent is:

1. A swimming pool monitor comprising an underwater microphone adapted to be submerged in said pool, said microphone producing electric signals in response to sound vibrations in said pool, alarm means, a detector circuit for actuating said alarm means only in response to signals from said microphone, a transducer for reconverting said signals into sound, means including a first switch means connected to pass signals from said microphone alternatively -to said detector circuit and to said transducer, an amplifying circuit connected between said microphone and said first switch means, said amplifying circuit including first and second filter means having wide and narrow pass band respectively, second switch means operative coincidental with said first switch means between two positions to feed the output of said microphone selectively to said first and second filter elements.

2. A swimming pool monitor comprising a first transducer for positioning in the water in said pool, said first transducer producing electric signals in response to sound vibrations in the pool, first amplifier means connected to the output of said transducer, said first amplifier means including switch means operative between two positions so as to feed the output of said first amplifier means selectively to said positions, second amplifier means connected to one position of said switch means, regenerative feedback means in said second amplifier means, said feedback means including a second switch operative coincidentally with said switch so as to disable said feedback circuit when said switch means is in its said one position and to enable said feedback circuit when said switch means is in its other said position, a second transducer connected to the output of said second amplifier means and a detector circuit connected between said other switch means position and said second ampli fier means, said detector circuit causing said second amplifier means to oscillate only upon arrival of signals from said first transducer.

3. A swimming pool monitor as defined in claim 2 wherein said first amplifier means includes a relatively wide band filter, a relatively narrow band filter and a switch operable coincidentally with said switch means so that the signal in said first amplifier means passes through said wide band filter when said switch means is in its said one position and passes through said narrow band filter when said switch means is in its said other position.

4. A swimming pool monitor as defined in claim 3 wherein the width of said narrow pass band is between 500900 cycles and said filter-preamplifier substantially excludes signals below 2500 cycles and the width of the wide pass band covers substantially the entire voice range of frequencies.

5. A swimming pool monitor as defined in claim 2 wherein said second amplifier means comprises at least a 'two stage amplifier and means including another switch for providing regenerative feedback in said second amplifier means when said switch means is in said other position.

'6. A swimming pool monitor as defined in claim 2 wherein said detector circuit comprises a flip-flop said flip-flop being in one state, control means connected between said flip-flop and said other switch means position for imposing a second state on said flip-flop only in response to signals from said first transducer and thereby actuating said second amplifier means, said flip-flop remaining in said second state even after cessation of said signals and means for returning said flip-flop to its said one state.

7. A swimming pool monitor as defined in claim 6 wherein said -fiip-flop comprises two transistors, one of said transistors being normally conducting, the other of said transistors being normally cut OE, and said control means includes a diode connected between said other switch means position and said one transistor and a relay coil connected in the circuit of said other transistor.

References Cited by the Examiner UNITED STATES PATENTS 2,435,996 2/1948 Baird 340-258 2,447,156 8/1948 Brittain. 2,709,251 5/1955 Schmidt 340-261 2,832,915 4/1958 McCoy 340-261 X 2,942,247 6/1960 Lineau 340-261 X 2,991,458 7/1961 Cooke 340-258 X 3,041,592 6/1962 Schmidt 340-258 3,049,699 8/1962 Larrick 340-276 X 3,069,673 12/ 196-3 Ward. 3,095,730 7/1963 Matheson. 3,109,165 10/1963 Bagno 340-258 3,128,456 4/1964 Sillirnan. 3,134,790 5/1964 Kelly 340-261 3,147,467 9/1964 Laaleman 340-261 FOREIGN PATENTS 942,848 11/1963 England.

NEIL C. READ, Primary Examiner.

R. M. GOLDMAN, Assistant Examiner. 

1.
 2. A SWIMMING POOL MONITOR COMPRISING A FIRST TRANSDUCER FOR POSITIONING IN THE WATER IN SAID POOL, SAID FIRST TRANSDUCER PRODUCING ELECTRIC SIGNALS IN RESPONSE TO SOUND VIBRATIONS IN THE POOL, FIRST AMPLIFIER MEANS CONNECTED TO THE OUTPUT OF SAID TRANSDUCER, SAID FIRST AMPLIFIER MEANS INCLUDING SWITCH MEANS OPERATIVE BETWEEN TWO POSITIONS SO AS TO FEED THE OUTPUT OF SAID FIRST AMPLIFIER MEANS SELECTIVELY TO SAID POSITIONS, SECOND AMPLIFIER MEANS CONNECTED TO ONE POSITION OF SAID SWITCH MEANS, REGENERATIVE FEEDBACK MEANS IN SAID SECOND AMPLIFIER MEANS, SAID FEEDBACK MEANS INCLUDING A SECOND SWITCH OPERATIVE COINCIDENTALLY WITH SAID SWITCH SO AS TO DISABLE SAID FEEDBACK CIRCUIT WHEN SAID SWITCH MEANS IS IN ITS SAID ONE POSITION AND TO ENABLE SAID FEEDBACK CIRCUIT WHEN SAID SWITCH MEANS IS IN ITS OTHER SAID POSITION, A SECOND TRANSDUCER CONNECTED TO THE OUTPUT OF SAID SECOND AMPLIFIER MEANS AND A DETECTOR CIRCUIT CONNECTED BETWEEN SAID OTHER SWITCH MEANS POSITION AND SAID SECOND AMPLIFIER MEANS, SAID DETECTOR CIRCUIT CAUSING SAID SECOND AMPLIFIER MEANS TO OSCILLATE ONLY UPON ARRIVAL OF SIGNALS FROM SAID FIRST TRANSDUCER. 